Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ACOUSTICAL INSULATING BARRIER
AND METHOD OF MAKING THE BARRIER
The present invention relates to acoustical
insulating barriers and methods of making the barriers,
and more particularly to such barriers which have
significant acoustical insulating properties to sounds
having a frequency between about 20 and 400 Hz, which
makes the insulating barrier particularly useful for
applications in automobiles and like devices.
BACKGROUND OF THE INVENTION
A wide variety of insulating barriers has been
proposed in the art for abating sound transmission from a
source thereof to some protected area or enclosure.
Notable examples of such sound barriers are those used for
abating sound through walls of houses, buildings and the
like, those used for abating sounds emanating from
highways and expressways, those used for abating sounds
from appliances, such as washing machines, dishwashers and
the like, and those used for abating sounds from the
exterior of an automobile to the interior of the
automobile. The sounds to be abated vary considerably with
the sources of the sounds, and such sounds can have quite
wide frequency ranges, commencing with only a few Hertz up
to thousands of Hertz. Thus, for every sound abatement
application, it is necessary to provide an acoustical
insulating barrier which is effective at the frequencies
expected from the sound to be abated. For example, the
usual sounds transmitted from the exterior of an
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automobile to the interior thereof generally have
frequencies from about 20 to 400 Hz. These sounds are
generated by tire and road noise, engine noise, wind
noise, noise from flexing of the automobile chassis or
body, and noise from vibrations of movable and static
mechanical components.
Accordingly, considerable effort has been expended in
the art to provide acoustical insulating barriers which
are effective in that frequency range, so that sound
abatement can be provided to the interior of an automobile
or like vehicle, although such acoustical insulating
barriers are useful in other applications, such as
dishwashers, washing machines, dryers, furnaces and like
appliances. It has been found that sounds in those
frequencies and up to frequencies of approximately 1000
Hz, and for some purposes up to 2000 Hz, are more
effectively abated by use of a high density material which
is, ideally, not in physical contact with the source of
the sound or an object which transmits the sound. For
example, the interior of an automobile is routinely
acoustically insulated from sound transmitted through the
floorboard, which sound originates from tires and road
noises, wind noises, engine noises, and noise from
vibration of mechanical and structural parts of the
automobile. To isolate the acoustical barrier from that
transmitting floorboard, to the extent possible, it is a
common practice in the art to provide a fibrous material
between the sound barrier and the floorboard. This
material dampens sound transmissions and mechanical
vibrations which would otherwise be transmitted directly
to and through the acoustical insulating barrier. Thus,
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direct physical contact of the sound barrier is avoided by
such material which spaces the acoustical insulating
barrier from the floorboard. A wide variety of such
materials has been used in the art, including non-woven
textile fabrics, particularly "shoddy" fabrics, foamed
polymeric materials, and the like. These materials are
referred to in the art as a "suspending layer".
Very typically, the high-density acoustical
insulating material is in the form of a layer of synthetic
material (sometimes referred to as %Nmastic"). That
synthetic material can take various forms, but typically
will be made of a bituminous material or a
bituminous/rubber material or a polymeric material which
is either dense in and of itself and/or has added thereto
densifying materials in order to be more effective in the
relevant frequencies.
Typically, the acoustical insulating barrier layer
(mastic) is glued to the suspending layer so that a
composite is formed of the insulating barrier layer and
suspending layer. In the case of an automobile, for
example, that composite acoustical insulating barrier is
placed under the cabin carpet of the automobile, although
it may also be placed under the felt or carpet used in the
trunk of the automobile or between the trunk liner and the
body of the automobile or between the head liner and the
roof of the automobile.
However, in each such application, in modern
automobile production, the automobile manufacturers
usually require that the supplier of the carpet, trunk
floor felt, etc., provide those units in a ready-to-be-
installed form. This means that each of the units, for
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example, the carpet covering the floorboard in front of
the driver and front passenger seat, has been molded to
the general configuration of that portion of the
floorboard and the acoustical barrier has been attached
thereto. This simplifies the assembly of the automobile,
in that the carpet and acoustical insulating barrier can
be quickly placed on the floorboard of the automobile
during assembly, and it will snugly fit the contours of
that portion of the floorboard. Hence, little time is
required in installing that portion of the
carpet/acoustical insulating barrier assembly.
In view of the foregoing, typically, a supplier of
the carpet for the automobile will adhesively bond the
acoustical insulating barrier, consisting of the barrier
layer and suspending layer, to the underside of the carpet
and then mold that assembly into the generally required
configuration, as explained above.
Since the acoustical insulating barrier layer is
glued to the suspending layer and the acoustical
insulating barrier layer is, in turn, glued to the
underside of the carpet, two different glue lines are
required for that assembly, with one glue line being
applied by the manufacturer of the acoustical insulating
barrier and another glue line being applied by the
manufacturer of the assembly of the carpet and the
acoustical insulating barrier.
Since all conventional glues of this nature contain
some fugitive component, e.g. solvent, for environmental
purposes, containment systems must be provided both in the
manufacture of the acoustical insulating barrier and in
the manufacture of the assembly of acoustical insulating
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barrier and carpet. This significantly increases the cost
of both of the acoustical insulating barrier and the
assembled acoustical insulating barrier and carpet.
In addition, since the prior art acoustical
insulating barrier layers are relatively heavy (typical
weights of about 12 to 14 ounces are per square foot), the
prior art acoustical insulating barriers made therewith
considerably contribute to an increased overall weight of
the automobile, which is quite undesirable.
Further, while the glue lines, as explained above,
are cured, solvent and other fugitive volatiles, i.e.
plasticizers, of the glue used in the glue line cannot be
totally removed during manufacture of the acoustical
insulating barrier or the assembly of the barrier and the
carpet. Those volatiles slowly evaporate from the
assembly, after being installed in the automobile, and
contribute to the well kiZown film of oily deposit that
collects on windshields, glasses, back windshields, door
panels and the like, especially, in a new automobile. The
automobile manufacturers have, of course, long sought
means of reducing that oily film, and the use of such glue
lines in the typical acoustical insulating barrier and the
assembled barrier and carpet only increase the incidents
of the oily film.
As illustrations of the prior art mentioned above,
U. S. Patent 4,056,161 to Allen discloses a sound barrier
having an outer layer of wear-resistant properties made of
a polymer, e.g. polyvinyl chloride, and a sound barrier
layer of high-density material filled with partieulate
material, such as barium sulfate. The sound barrier layer
is preferably a vinyl plastisol. In turn, the sound
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barrier layer is bonded to a suspending layer at its
undermost side, which suspending layer is preferably a
polyurethane foam. The composite is bound together by
heating the composite and allowing the vinyl plastisol of
the barrier layer to bond the three layers together. This
older product, however, has the disadvantages described
above in that the composite assembly is essentially that
of an adhesive operation via the vinyl plastisol, and off-
gassing of condensable volatiles from that vinyl plastisol
can be considerable, which is quite undesired, as noted
above.
U. S. Patent 4,966,799 discloses an automobile sound
barrier made of fibers and filled with a filler. It is
adhesively bonded to a suspending layer and can include a
carpet for the automobile. Here again, adhesive bonding of
the layers is required.
U. S. Patent 5,266,143 is directed to an automobile
sound barrier where a substrate of an elastomer or
synthetic rubber, which is filled with a filler, is bonded
to a porous fibrous layer by adhesion bonding.
U. S. Patent 5,068,001 describes a sound barrier for
automobiles, where a fibrous core is adhesively bonded to
fibrous reinforcing mats on each side of the core by way
of coating the reinforcing mats with uncured thermosetting
resin and molding the composite in a heated mold where the
thermosetting resin is cured.
In view of the above-discussed state of the art, it
would be a substantial advantage in the art to provide an
acoustical insulating barrier which can provide the
acoustical insulation of the prior art acoustical
insulating barrier, as described above, but which does not
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require glue for production of the barrier or for the
assembly of the barrier and carpet, and, hence, avoid the
costly environmental containment required by the barrier
manufacturer and the manufacturer of the carpet and
barrier assembly, as well as reduce oily volatiles. In
addition, it would be a considerable advantage to the art
to provide an acoustical insulating barrier which can
abate sound as well as the conventional barrier, but with
considerably less weight per square unit (lower density)
and at a considerably lower cost per square unit.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is based on several primary and
subsidiary discoveries.
As a first primary discovery, it was found that an
acoustical insulating barrier could be prepared without
adhesive bonding, e.g. without a glue line, between the
barrier layer and the suspending layer, and thus obviate
the problems associated therewith, as described above.
According to the invention, the barrier layer and
suspending layer can be attached to each other, thus
forming the acoustical insulating barrier, by a plurality
of needled stitches passing through the barrier layer and
the suspending layer. This eliminates the need for
adhesive bonding, i.e. the glue line, between the barrier
layer and the suspending layer. As a subsidiary discovery
in this regard, it was found that if the suspending layer
is of certain thicknesses and densities, such needling can
be achieved so as to firmly lock the barrier layer to the
suspending layer but at the same time not decrease the
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suspending properties of the suspending layer, as
described above.
As another primary discovery, it was found that the
needled stitches could be provided by a layer of
needleable textile fibers disposed on the barrier layer so
that the needleable textile fibers of that layer form the
stitches which pass through the barrier layer. As a
subsidiary discovery in this regard, it was found that
such needling can take place from that layer of needleable
textile fibers when that layer of fibers is of certain
thicknesses and densities.
As a further subsidiary discovery, it was found that
a layer of such needleable textile fibers may be placed
both on and under the barrier layer and needling can be
performed from both the top and bottom of the acoustical
barrier to provide increased consolidation of the
acoustical barrier during needling thereof.
Thus, as can be appreciated from the above, in the
present acoustical barrier, there is a first layer of the
needleable textile fibers disposed on the top of the
barrier layer, and the barrier layer is disposed on the
second suspending layer, i.e. the barrier layer is
disposed between the first needleable textile fiber layer
and the second suspending layer. However, in this regard,
it was found that with such a sandwiched arrangement of
the barrier layer, the barrier layer must have certain
thicknesses and certain densities and comprise a
substantially continuous film of high-density needleable
polymeric material. With such a barrier layer, the
stitches, formed from the first fiber layer of needleable
textile fibers, can pass through that barrier layer and
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into the second suspending layer so as to bind the first
fiber layer, the barrier layer and the second suspending
layer into a composite which is sufficiently consolidated
as to be easily handleable and manipulatable in attaching
that assembled acoustical barrier to an underside of an
automobile carpet or felt and place such an assembly in an
automobile without any separation of the layers of the
acoustical barrier.
As another primary discovery, it was found that when
the first layer of needleable textile fibers also contains
heat-fusible fibers, then the produced acoustical barrier
can be heat fused to the underside of the carpet or felt,
thus eliminating the glue line between the acoustical
barrier and the underside of the carpet or felt.
Accordingly, briefly stated, the present invention
provides a composite acoustical barrier. That acoustical
barrier has a non-woven first layer of needleable textile
first fibers. That first layer has a thickness of between
about 0.01 inch and 0.5 inch and a density of between
about 1 and 10 lbs. per cubic foot.
There is also provided a non-woven low-density second
layer of textile fibers (which forms the suspending
layer). That second layer has a thickness of between about
0.2 inch and 5 inches and a density of between about 0.1
and 4.0 lbs. per cubic foot.
A high-density acoustical barrier layer is disposed
between the first and second layers. That intermediate
barrier layer has a thickness of between about 0.01 inch
and 0.5 inch and a density of at least about 50 lbs. per
cubic foot, e.g. up to as much as 200 lbs. per cubic foot.
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That barrier layer comprises a substantially continuous
film of high-density needleable polymeric material.
There are a plurality of needled stitches formed from
the first fibers and extending from the first layer
through the intermediate barrier layer and at least into
the second layer.
There is also provided a method of producing a
composite acoustical barrier. In that method, a composite
is assembled of (i) a non-woven first layer of needleable
textile first fibers, which first layer has a thickness of
between about 0.01 inch and 0.5 inch and a density of
between about 1 and 10 lbs. per cubic foot; (ii) a non-
woven, low density second layer of textile second fibers
(the suspending layer), which second layer has a thickness
of between about 0.2 inch and 5 inches and a density of
between about 0.1 and 4.0 lbs. per cubic foot; and (iii) a
high density intermediate acoustical barrier layer
disposed between the first and second layers, which
intermediate barrier layer has a thickness of between
about 0.01 inch and 0.5 inch and a density of at least
about 50 lbs. per cubic foot, e.g. up to as much as 200
lbs. per cubic foot, and which barrier layer comprises a
substantially continuous film of high density needleable
polymeric material.
That composite is needled with about 100 to about 600
stitches per square inch, such that stitches formed from
the first fibers extend from the first layer, through the
intermediate barrier layer, and at least into the second
layer.
Here again, preferably, that first layer contains
heat-fusible fibers, such that the acoustical barrier can
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be heat fused to the underside of a carpet or felt, and
thus eliminate the adhesive bonding, i.e. glue line, of
the prior art in that position.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatic cross-section of a typical
prior art acoustical barrier glued to the underside of an
automobile carpet;
Figure 2 is a diagrammatic cross-section of an
embodiment of the present acoustical barrier fusion bonded
to the underside of an automobile carpet;
Figure 3 is a block diagram of the steps of the
present process;
Figure 4 is a diagrammatic cross-section of a
sheath/core fiber used in an embodiment of the present
acoustical barrier;
Figure 5 is a diagrammatic cross-section of a
bicomponent fiber used in an embodiment of the present
acoustical barrier; and
Figure 6 is a graph comparing the acoustical response
of the prior art acoustical barrier with the response of
the present acoustical barrier.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As background to the present invention, Figure 1 is a
diagrammatic cross-section of a typical prior art
acoustical barrier glued to the underside of an automobile
carpet. That figure shows the acoustical barrier,
generally 1, glued to a carpet 2 at the underside 2a
thereof by way of a glue line 3. The acoustical barrier,
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generally 1, has a barrier layer 4 glued to a suspending
layer 5 by way of a second glue line 6.
Asnoted above, in the prior art, the acoustical
barrier 1 was produced by providing the suspending layer
5, placing a glue line 6 on a top surface 7 thereof and
adhering the barrier layer 4 thereto by curing of that
glue line 6. The manufacturer of the carpet assembly
places a glue line 3 on the upper surface 8 of barrier
layer 4 or the underside 2a of carpet 2 and then glues the
underside 2a of carpet 2 to the barrier layer 4 by way of
the glue line 3. In one conventional application of the
prior art acoustical barriers, a so-called "mastic back"
is applied to the underside 2a of carpet 2 which also
functions as the glue line 3 and provides an acoustical
barrier layer at the same time.
However, substantial problems exist in this prior art
arrangement. First of all, the use of those two glue
lines, i.e. glue lines 3 and 6, provides undesirable
sources of off-gassing of fugitive or volatile glue
components which can condense on the interior of the
automobile after manufacture, as described above. This is
quite undesirable. Secondly, it is very difficult to glue
typical prior art barrier layers 4 to either the
suspending layer 5 or the underside 2a of carpet 2.
Therefore, the glue bond between carpet 2 and acoustical
barrier 1 is a very unreliable bonding, and it is not
unusual for the acoustical barrier 1 to separate from the
carpet 2 when being installed in an automobile, which
requires special and time-consuming hand labor for
adequately installing the combination of carpet 2 and
acoustical barrier 1 when those two have separated.
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In addition, when the manufacturer assembles the
combination of the acoustical barrier 1 and the carpet 2,
the correct configuration for a particular automobile is
cut from a supply of acoustical barrier 1 and a supply of
carpet 2. When gluing acoustical barrier 1 and carpet 2
together, glue line 3 must be hand applied, e.g. by
spraying, and this greatly increases the cost of the
assembly of the carpet 2 and acoustical barrier 1 and also
entails considerable and difficult environmental
constraints, as noted above.
In addition, the same sort of difficulties are
encountered in gluing barrier layer 4 to the suspending
layer 5, and an unreliable glue bond often results.
Further, the same hand labor and environmental
considerations are involved in that glue line.
Further, in order to improve, to the degree possible,
the adhesion of both the barrier layer 4 to the suspending
layer 5 and the acoustical barrier 1 to the underside 2a
of carpet 2, both glue lines 3 and 6 must be fairly
thickly applied, and this increases the weight of the
assembly. It is not unusual for an assembly of that nature
with such glue lines to have a weight of about 14 ounces
per square foot. In view of the number of square feet
involved in carpeting an automobile, this weight
considerably increases the overall weight of the
automobile, which is quite undesirable.
Additionally, since the prior art acoustical barrier
1 and the assembly with carpet 2 require the glue lines 3
and 6, and in view of the difficulties of reliable glue
bonding, as noted above, substantial limitations are
placed on the materials which may be successfully used as
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the barrier layer 4. Those prior art barrier layers were
often referred to as "mastics", since they resembled
and/or in part are bituminous products which are also
sources of condensable volatiles, as explained above.
Figure 2 is a diagrammatic cross-section of the
present acoustical barrier fusion bonded to the underside
of an automobile carpet. As shown in that figure, the
acoustical barrier, generally 10, is bonded to a carpet 12
at its underside 12a, but it will be noted that no glue
line is involved therewith, as explained below. The
acoustical barrier of the present invention has a non-
woven first layer 13 of needleable textile first fibers
13a, a non-woven low density second layer 15 (suspending
layer) of textile second fibers 15a, and a high density
intermediate acoustical barrier layer 14.
There are a plurality of needled stitches 19 formed
from the first fibers 13a that extend through the first
layer 13, through the intermediate barrier layer 14 and at
least into the suspending second layer 15.
The first layer 13 is relatively thin, since a major
purpose of that layer is to provide first fibers 13a for
forming stitches 19. In addition, as explained more fully
below, the first fibers 13a of first layer 13 provide
fusion bonding between acoustical barrier 10 and the
underside 12a of carpet 12 by use of fusible fibers
instead of a glue line. That fusion bonding, also,
requires only a thin layer of the first fibers 13a. Thus,
the first layer 13 has a thickness of between about 0.01
inch and 0.5 inch, preferably about 0.05 and 0.1 inch and
a density of about 1 and 10 lbs. per cubic foot, more
preferably about 3 to about 5 lbs. per cubic foot. This
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will provide sufficient first fibers 13a to form stitches
19 and to provide the fusion bonding between acoustical
barrier 10 and carpet 12, as explained more fully below.
If the thickness of first layer 13 is too great, then the
fusion bonding between acoustical barrier 10 and carpet 12
can be compromised, and, moreover, is an expensive waste
of fibers and unnecessarily increases the overall weight
of the acoustical barrier 10. On the other hand, there
must be sufficient first fibers 13a in first layer 13 to
adequately form stitches 19 and to perform that fusion
bonding function. It is for these reasons that the
thickness and densities of first layer 13, defined above,
are required.
The second layer 15 must provide the suspending
function, as described above, and in order to achieve that
task, the second layer 15 must have certain thicknesses
and densities. In addition, second layer 15 must
adequately engage and hold stitches 19 therein, so as to
adequately bind the composite together. Thus, in the
present invention, the suspending second layer 15 has a
thickness of between about 0.2 inch and 5 inches,
preferably between about 0.5 inch and 3 inches, and a
density of between about 0.1 and 4.0 lbs. per cubic foot,
preferably about 1.0 to 2.0 lbs. per cubic foot.
The high-density intermediate acoustical barrier
layer 14, as noted above, is disposed between the first
and second layers 13 and 15. That intermediate barrier
layer 14 must have sufficient thickness and density (total
mass) so as to act as an acoustical barrier, but, on the
other hand, that barrier layer 14 must also be needleable,
in order that stitches 19 may pass therethrough without
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substantially disrupting barrier layer 14. Thus, for these
dual purposes, the barrier layer has a thickness of
between about 0.01 inch and 0.5 inch and a density of at
least 50 lbs. per cubic foot, preferably between about 100
and up to 200 lbs. per cubic foot, e.g. between 100 and
150 lbs. per cubic foot.
As opposed to the barrier layer of the prior art, the
present barrier layer 14 is a substantially continuous
film of high-density needleable polymeric material, as
explained in more detail below.
The plurality of needled stitches 19, which are
formed from the first fibers 13a and extend from first
layer 13 through intermediate barrier layer 14 and at
least into second layer 15, must bind together all of
first layer 13, barrier layer 14 and suspending second
layer 15 in such a manner that those layers become so
consolidated that the acoustical barrier 10 can be
handled, shipped, cut, conformed, molded and fusion bonded
to the carpet 12 without the three layers becoming
disrupted or substantially disengaged. On the other hand,
the number of stitches 19 cannot be so great that the
barrier layer 14 is substantially deteriorated from an
acoustical attenuation point of view. Generally speaking,
to achieve these results, the number of stitches 19 are
from about 100 to about 600 stitches per square inch of
the acoustical composite, and more preferably from about
150 to 500 or about 200 to 400 stitches per square inch of
the acoustical composite.
The first fibers 13a, as noted above, must be
needleable fibers in order to form stitches 19. Those
first fibers 13a forming first layer 13 can be carded
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fibers or a needleable web of fibers. Thus, the first
fibers l3a can simply be carded onto barrier layer 14, as
explained in more detail below in connection with the
process, or those first fibers 13a may simply be a pre-
formed needleable web of fibers which is doffed onto
barrier layer 14, again as explained in more detail below
in connection with the process. However, to ensure that
those first fibers 13a will adequately needle into
stitches 19, those first fibers 13a should have a denier
per filament of between about 1 and 35 and, preferably, a
length between about 0.1 inch and 5 inches, preferably
between about 1 inch and 3 inches. This ensures sufficient
mobility of the fibers 13a that they can be engaged by the
barbs of needles so as to form adequate stitches 19.
Almost any needleable textile fiber may be used for
those first fibers 13a, since it is only the physical
characteristics of the fiber, and not the chemical
composition thereof, which is important. However, very
conveniently, the first fibers l3a are chosen from one or
more of polyester, polyolefin, cellulosic, polyamide,
nylon, polyacrylic, aramid, imide, melamine fibers and
polyvinyl chloride fibers (PVC).
In order to eliminate glue line 3 of the prior art,
which adheres the acoustical barrier 1 of the prior art
(see Figure 1) to carpet 2, the present first layer 13 of
the present composite should have as part of that layer a
heat-fusible component 13b which is heat fusible at a
temperature above 180 F and contained in the first layer 13
in an amount of between about 10% and 70% by weight,
preferably about 20% to 60% by weight, of the first layer
13. With such a fusible component 13b in first layer 13,
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after the present acoustical barrier 10 and carpet 12 are
cut to be configured for the particular automobile, carpet
12, or the assembly of carpet 12 and acoustical barrier
10, or one or the other thereof, is heated and pressed in
a configuring mold to mold the assembly of the carpet and
acoustical barrier into a configuration generally along
the lines of the configuration of the portion of the
automobile which that assembly is to cover, e.g. the front
floorboard of an automobile. This is a usual procedure in
the prior art. However, when present first layer 13
includes a fusible component 13b, and when that molding is
carried out (usually at temperatures in excess of 180 F),
the fusible component 13b in first layer 13 will tackify
or melt, and when pressed in the mold, that fusible
component 13b will fuse acoustical barrier 10 to the
underside 12a of carpet 12 and thereby eliminate the glue
line 3 of the prior art. The fusible component, not
carrying solvents, extenders, or fugitive plasticizers and
the like, will not contain volatile components and,
therefore, avoids the off-gassing and oily condensation in
the automobile, as explained above.
The fusible component 13b can be any of the usual
fusible components, such as polyolefins or polyvinyl
chlorides and the like. Most preferably, the heat-fusible
component 13b is in a heat-fusible fiber form, e.g. the
heat-fusible fiber form is a bicomponent fiber or a
sheath/core fiber. Figure 4 is a diagrammatic cross-
section of a sheath/core fiber having a core 40 and a
sheath 41. Typically, such a fiber will have a core 40 of
polyester, cellulose, nylon and the like, as set forth
above, and the sheath 41 will be the fusible component,
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e.g. a polyolefin or polyvinyl chloride. Alternatively,
the heat-fusible fiber may be a bicomponent fiber, as
shown in Figure 5, where one component 50 is the heat-
fusible component, as described above, and the second
component 51 is also as described above, e.g. polyester
fiber and the like. Alternatively, separate non-fusible
and fusible fibers may be used.
As can be appreciated, when a fusible component 13b
is used to adhere acoustical barrier 10 to carpet 12, the
first layer 13 cannot be too thick, since if it is, that
layer could separate during handling, forming and the like
of the acoustical barrier 10 or when applied to or when
handling of the assembly with carpet 12. Therefore, it is
preferable that that first layer 13 has a thickness of
between about 0.01 and 0.5 inch, and more preferably
between about 0.05 and 0.1 inch. This provides a tight
first layer 13 but yet with sufficient fibers and depth of
fibers to achieve stitches 19 by barbs of needles picking
up the fibers to form stitches. This is particularly true
when the first layer 13 has a density of between about 3
and 5 lbs. per cubic foot.
The suspending second layer 15 also may be in the
form of carded fibers or a needleable web of fibers, as
explained above in connection with first layer 13.
However, the second fibers 15a, in order to provide the
suspending function as described above, should have much
higher deniers than the first fibers 13a of the first
layer 13, and particularly deniers per filament of at
least 5 and up to as much as 70, e.g. 15 to 60 denier per
filament. The lengths of the second fibers 15a can be from
about 0.5 to about 5 inches. Here again, the particular
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second fibers 15a, as with the first fibers 13a, are not
critical from a chemical point of view, but are only of
concern in connection with the above-noted function and
mechanical aspects thereof, e.g. providing the suspending
function. Thus, any composition may be used, but here
again, the second fibers 15a may be one or more of
polyester, nylon, polyolefin, cellulosic, polyamide,
polyacrylic, aramid, imide, melamine and polyvinyl
chloride (PVC) fibers.
Second layer 15, which provides the suspending
action, as noted above, can have a thickness of between
about 0.2 inch and 5 inches and a density of between about
0.1 and 4.0 lbs. per cubic foot, while still allowing the
stitches to pass therethrough and supply the suspending
function. However, more preferably, the thickness of the
second layer 15 is between about 0.5 inch and 3 inches and
the density is between about 1.0 and 2.0 lbs. per cubic
foot. This will ensure that the stitches 19 may easily
pass therethrough and still provide the required
suspending function.
However, as can be appreciated from these thicknesses
and densities, second layer 15 is not a very consolidated
layer, and to ensure that second layer 15 retains
consolidation during handling, forming and the like,
again, it is preferred that the second layer 15 include a
heat-fusible component 15b which is heat fusible at
temperatures above about 180 F and is contained in the
second layer 15 in amounts of between about 5% and 40% by
weight of the second layer 15, especially between about
10% to 30% by weight. Here again, the heat-fusible
component is preferably in a heat-fusible fiber form, and
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more preferably, the heat-fusible fiber form is a
bicomponent fiber or a sheath/core fiber, as shown in
Figures 4 and 5, with the same or similar compositions as
described above. Separate fusible and non-fusible fibers,
however, may be used. However, in connection with the
second layer 15, it is preferred that the heat-fusible
fiber is a sheath/core fiber, since this will ensure
fusing of the fibers 15a of second layer 15 at crossover
points of fibers within second layer 15. Fusing of the
fusible component 15b may take place when forming
suspending layer 15, or forming acoustical barrier 10 but
it can, although less desirably, take place when
acoustical barrier 10 is fusion bonded to carpet 12, as
explained above in connection with the molding process.
However, it is preferred that fusing of the fusible
component take place prior to needling for the reasons
explained below.
The barrier layer 14, disposed between the first and
second layers 13 and 15, must be a high density needleable
polymeric material, as noted above, in order to attenuate
sound of the relevant frequencies and allow the binding of
the first and second layers with the barrier layer during
the needling operation. Also as noted above, in order to
attenuate acoustical sounds of the relevant frequencies,
the density of the barrier layer 14 must be at least 50
lbs. per cubic foot and have a thickness of between 0.01
inch and 0.5 inch, but more preferably, to achieve these
results, the barrier layer 14 has a thickness of between
about 0.01 inch and 0.15 inch and a density of between
about 100 and 150 lbs. per cubic foot. This will ensure
adequate sound attenuation of the relevant frequencies and
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yet ensure adequate needling of the polymeric material for
binding of the three layers. Of course, the density and
the needleability of the barrier layer 14 will depend, to
some extent, on the polymeric material chosen for the
intermediate barrier layer. While a wide variety of
polymeric materials are acceptable for the barrier layer,
and the particular polymeric material is not critical,
particularly good polymeric materials for the barrier
layer 14 are one or more of rubber, synthetic rubbers,
polyvinyl chloride (preferably with a polymerizable
plasticizer), polyvinyl acetate, polyurethane, silicone
rubber, polyethylenevinyl acetate and a polymer of
ethylene-propylene dimer monomer (EPDA). These materials
have special advantages in that they are soft enough to
allow needle penetration without significantly tearing the
material or breaking needles and, after the needles have
been withdrawn, the material will substantially reseal the
needle punched holes made by the needles due to the soft
elastic nature of the polymeric material. As one skilled
in the art readily appreciates, the existence of holes in
the barrier layer decreases the sound abatement of that
barrier layer in the relevant frequencies. With these
softer and yieldable materials, the needle punch holes in
the barrier layer 14 are largely resealed by the
elastomeric movement of the soft material once the needles
have been withdrawn therefrom. However, it is not
necessary that the polymeric material have this latter
property, since the needle punched holes, as noted above,
are a relatively small number per square inch, and even if
the polymeric material does not reseal the holes by
elastomeric movement, the sound abatement at the relevant
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frequencies of the barrier layer will still be quite
substantial.
The barrier layer 14 must, of course, have a high
density, as noted above, so as to achieve sound abatement
at the relevant frequencies. Lower densities require
barrier layers of too great a thickness to achieve
adequate total mass for adequate sound abatement.
Normally, a polymeric material of the above-described
nature, which forms the barrier layer 14, will not have
densities as high as that desired. As is common in the
art, such barrier layers are increased in density by the
addition of a filler 23 thereto, and particularly a solid
particulate filler, and especially a solid particulate
material having a density greater than 1 gram per cubic
centimeter. Generally, these fillers 23 are inorganic
fillers, such as clay, metal or a metal compound, for
example, kaolin clay and barium sulfate, although other
high-density fillers may equally be used. The particular
filler is not critical, and any of the prior art fillers
may be used. With such fillers 23, the barrier layer 14
may have a density between about 50 and 200 lbs. per cubic
foot, which is quite desirable for the relevant
frequencies. Of course, for uniform sound abatement, the
filler 23 is uniformly dispersed within the barrier layer
14. Such fillers 23 also provide some additional toughness
to the polymeric material, which will ensure the ability
of the needles to penetrate deeply into the second layer
15 and preferably extend all the way through the second
layer 15, as shown in Figure 2, without substantially
disrupting the barrier layer 14. Even more preferably, as
shown in Figure 2, when the stitches penetrate beyond a
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lowermost surface 20 of second layer 15, the stitches can
form a knot 21 of fibers outside of that lowermost surface
20 which further locks stitches 19 into place and which,
consequently, locks all of layers 13, 14 and 15 together
in a very consolidated acoustical barrier 10.
With an acoustical barrier 10, as described above,
the composite of that acoustical barrier is easily fusion
bonded at the top surface 22 of first layer 13 to the
underside 12a of the carpet or felt 12 by the heating and
molding technique described above in producing an
automotive carpet or felt, i.e. the composition is fusion
bonded to the carper or felt 12 by way of a heat-fusible
component 13b of the first layer 13.
Turning now to the method of the invention, and as
diagrammatically illustrated in Figure 3, the method
comprises assembling of a composite of (i) the non-woven
first layer 13 of needleable textile first fibers 13a,
(ii) the non-woven low density second layer 15 of textile
second fibers 15a, and (iii) the high-density intermediate
acoustical barrier layer 14, which is disposed between the
first and second layers 13, 15. This assembly of the
composite may be carried out in a number of different
ways. For example, the various layers may be assembled
from pre-formed layers thereof simply by unrolling those
pre-formed layers and placing the layers in the correct
order, as described above. Alternatively, second layer 15
may be formed simply by carding fibers 15a from a supply
thereof onto a conventional apron. A pre-form of the
barrier 18 can then be unrolled and placed thereon.
Likewise, the first layer 13 can be formed by carding
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fibers 13a onto the top of barrier layer 14, also while
the second layer 15 and barrier layer 14 are on the apron.
Alternatively, second layer 15 may be a pre-form
(preferably pre-heated to fuse fusible component 15b), and
barrier layer 14 may be placed thereon as a pre-form or by
conventional coating or extrusion techniques, e.g. from a
heated thermoplastic form of barrier layer 14, such as
polyvinyl chloride. Of course, that polymeric material
will contain the fillers 23 described above. A coating or
extrusion can be arranged to coat essentially only onto
the topmost surface of second layer 15 (by flowing the
coating or extrudant onto second layer 15) or it can be
arranged to penetrate to a controlled depth into the
topmost surface of layer 15 (by doctor blade coating of
that layer). In these techniques, therefore, barrier layer
14 will contain some of the fibers of second layer 15 and
reinforce barrier layer 14 for added strength. Also, some
locking of barrier layer 14 to the second layer 15 will
occur by those fibers being within barrier layer 14. When
a pre-form of barrier layer 14 is used, that pre-form may
also contain fibers for such reinforcing purposes.
However, reinforcing fibers are not required and would
only be used, essentially, for special purposes where
additional strengths are required.
However, since a coating or extrusion technique
requires additional equipment and environmental concerns,
that is not the preferred form of the process.
The preferred form of the process is where first
layer 13 and second layer 15 are either pre-formed or
carded, as described above, and barrier layer 14 is a pre-
form thereof.
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After the assembly of the composite, the composite is
needled with about 100 to 600 stitches per square inch,
especially 150 to 500 and more preferably 200 to 400
stitches per square inch, in a conventional needle loom.
Since it is only necessary to needle from one side of the
composite (from the side of first layer 13) to consolidate
that composite with stitches 19, a single-board loom may
be used or only one board of a double-board loom. That
needling, however, must be such that the stitches 19
formed from the first fibers 13a extend from the first
layer 13 through the intermediate barrier layer 14 and at
least into the second layer 15, and preferably through the
second layer 15 to the lowermost surface 20 thereof, in
order to, preferably, form knots 21.
When additional strength of the composite is required
for special purposes, an additional layer or layers,
similar to first layer 13, may be carded or laid on the
top or bottom of second layer 15 (shown in Figure 2 as
layers 30, 31) and needling is performed from both sides
of the barrier 10, e.g. in a double-board loom to form
stitches (partially shown) from the opposite side of the
composite, i.e. from lowermost surface 20 or from the
underside of barrier layer 14. However, in such case,
preferably, second layer 15 has the fusible component 15b
fused so that little or no fibers from second layer 15
form stitches in this alternative embodiment.
Alternatively, any fusible component 15b in second
layer 15 may be unfused during needing and needling is
carried out from both sides of barrier layer 14. In this
case, fibers from second layer 15 form some stitches. The
needles forming stitches from second layer 15 should be
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less aggressive and fewer in number so as to not disrupt
second layer 15. This needling, however, does provide a
very well consolidated composite.
In the most preferred form of the process, first
layer 13 is laid onto the top of barrier layer 14 either
as a carded or a pre-formed layer, but in the case of a
pre-formed layer, the fibers 13a must be sufficiently
mobile during the needling operation such that the fibers
13a can be formed into stitches 19 and the composite
needled as described above, and especially from both sides
of the barrier layer 14. To ensure that mobility and form
adequate stitches, the first layer 13 must have the
thicknesses and densities described above.
After the acoustical barrier 10 is formed, that
barrier 10 is fusion bonded to the carpet or felt 12 by
the molding technique described above.
The invention will now be illustrated by the
following example where all percentages and parts are by
weight unless otherwise indicated, as is the same in the
specification and claims.
EXAMPLE
A pre-formed suspending layer was purchased from the
W. T. Burnett Company, and was composed of 15 denier per
filament polyester fibers and a polyester/polyolefin
sheath/core binder fiber, which had been fused in the
layer. The binder fiber was 15% of the layer and the
polyester fiber was 85% of the layer. The layer was 2
inches thick and had a density of 0.58 lbs. per cubic
foot.
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The first layer was made by carding a combination of
50% of the same binder fibers, 6 denier per filament and 2
inches average length, and 50% polyester fibers, 25 denier
per filament and 2 inches average length. The density was
about 2.7 lbs. per cubic foot.
A barrier layer was produced by Beckwith-Bemis
Company from extruded polyvinyl chloride with 40% kaolin
clay in fine particulate form so as to provide a barrier
layer with a density of about 125 lbs. per cubic foot.
In the process, the first layer was carded as a web
onto a conveyor apron by a camel back cross lapper to
accumulate a web weight of about 0.2 ounce per square
foot.
The barrier layer with a weight of about 9 ounces per
square foot was unrolled onto the first layer on the
conveyor apron.
A second layer of fine fibers which was the same as
the first layer was carded onto the barrier layer.
The suspending layer with a weight of about 1.5
ounces per square foot was unrolled onto the top of the
second fine fiber layer while on the conveyor apron.
The so-assembled layers were conveyed on the conveyor
apron to a compressive batt feeder which compressed the
assembly sufficiently to feed the assembly into a
conventional needle loom.
The needle loom was a Shoou Shyng SDP 250 H 2x2. The
speed of feed of the assembly through the loom was 11
linear feet per minute. The loom was set to run at 650 RPM
with needle penetrations of 4 mm at the top of the
assembly and 12 mm at the bottom of the assembly. The
needles of the A/B boards (top boards) were loaded at 33%
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of capacity with Groz Beckert F333 needles and the C/D
boards (bottom boards) were loaded at 16% of capacity with
Groz Beckert C222 needles.
The needled acoustical barrier had a thickness of
about 0.75 inch and a weight of about 11 ounces per square
foot.
The acoustical barrier was attached to a conventional
automobile carpet by further bonding and tested for
acoustical attenuation in a conventional sound
transmission loss room (conventionally used by automobile
manufacturers for testing acoustical barriers), along with
an identical test of a conventional sound barrier glued to
a conventional automobile carpet, which consisted of a
cotton suspending layer and a back mastic applied to the
underside of the carpet to which the conventional sound
barrier was applied. The results are shown in Figure 6,
where the dashed line is the conventional barrier (about
15 ounces per square foot), and the two solid lines are
the present barrier/carpet assembly. All tests were run at
a simulated 45-MPH speed. The conventional barrier/carpet
and one test of the present barrier/carpet were
"midseat center" tests and one test of the present
barrier/carpet was a "rear seat center" test.
As can be seen from Figure 6, all three tests
produced essentially the same results. Thus, the present
invention can achieve sound abatement equally well as
conventional acoustical barriers, but without the
conventional glue lines and with reduced weight.
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